package com.milo.common.utils;

import org.springframework.web.multipart.MultipartFile;
import sun.misc.BASE64Decoder;

import java.io.*;

/**
 * <p>
 *    适用类型
*  1.txt      data:text/plain;base64,
*  2.doc     data:application/msword;base64,
 * 3.docx   data:application/vnd.openxmlformats-officedocument.wordprocessingml.document;base64,
 * 4.xls      data:application/vnd.ms-excel;base64,
 * 5.xlsx    data:application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;base64,
 * 6.pdf     data:application/pdf;base64,
 * 7.pptx   data:application/vnd.openxmlformats-officedocument.presentationml.presentation;base64,
 * 8.ppt     data:application/vnd.ms-powerpoint;base64,
 *
 * 图片
 * 1.png      data:image/png;base64,
 * 2.jpg       data:image/jpeg;base64,
 * 3.gif        data:image/gif;base64,
 * 4.svg      data:image/svg+xml;base64,
 * 5.ico       data:image/x-icon;base64,
 * 6.bmp     data:image/bmp;base64,
 * </p>
 * Base64编码的文件转回MultipartFile
 * @author Milo Lee
 * @date 2021-12-03 17:18
 *
 */
public class BASE64DecodedMultipartFile implements MultipartFile {
  
    private final byte[] imgContent;
    private final String header;
  
    public BASE64DecodedMultipartFile(byte[] imgContent, String header) {
        this.imgContent = imgContent;
        this.header = header.split(";")[0];
    }
  
    @Override
    public String getName() {
        return System.currentTimeMillis() + Math.random() + "." + header.split("/")[1];
    }
  
    @Override
    public String getOriginalFilename() {
        return System.currentTimeMillis() + (int) Math.random() * 10000 + "." + header.split("/")[1];
    }
  
    @Override
    public String getContentType() {
        return header.split(":")[1];
    }
  
    @Override
    public boolean isEmpty() {
        return imgContent == null || imgContent.length == 0;
    }
  
    @Override
    public long getSize() {
        return imgContent.length;
    }
  
    @Override
    public byte[] getBytes() throws IOException {
        return imgContent;
    }
  
    @Override
    public InputStream getInputStream() throws IOException {
        return new ByteArrayInputStream(imgContent);
    }
  
    @Override
    public void transferTo(File dest) throws IOException, IllegalStateException {
        new FileOutputStream(dest).write(imgContent);
    }

    public static MultipartFile base64ToMultipart(String base64) {
        try {
            String[] baseStrs = base64.split(",");

            BASE64Decoder decoder = new BASE64Decoder();
            byte[] b = new byte[0];
            b = decoder.decodeBuffer(baseStrs[1]);

            for (int i = 0; i < b.length; ++i) {
                if (b[i] < 0) {
                    b[i] += 256;
                }
            }
            return new BASE64DecodedMultipartFile(b, baseStrs[0]);
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }
  
}